Owner's Problem Description
The owner describes a 1992 Honda Prelude with an automatic transmission and 181,000 miles experiencing harsh jerking and vibrations when placed in gear, especially noticeable at idle. While driving, vibrations decrease significantly. Observed severe exhaust vibrations when in drive with brakes applied. The vehicle has recently been tuned up, and the owner is awaiting a replacement engine mount for one that is broken. The owner is seeking further diagnostic help.
Professional Technical Analysis
The vehicle in question is a 1992 Honda Prelude with an automatic transmission and approximately 181,000 miles. The symptoms presented include severe vibrations and jerking when the vehicle is placed in any gear, particularly at idle. While driving, the vibrations diminish significantly, which suggests a potential issue primarily associated with the engine and transmission mounts. The owner has noted that the exhaust system vibrates excessively when the vehicle is in drive with the brakes applied. Recent maintenance included a full tune-up, but the vehicle is still waiting for a replacement engine mount, which has been confirmed as broken. This indicates that the engine mount's failure could lead to excessive engine movement, contributing to the vibrations felt throughout the vehicle. The harsh jerking could also suggest a possible issue with transmission engagement or fluid condition, particularly if the transmission feels like it slips slightly during acceleration from a complete stop. Performing a thorough inspection of all engine and transmission mounts is critical, including checking for any additional damaged mounts that could exacerbate the vibration issues. Additionally, inspecting the condition of the transmission fluid for contamination or low levels is essential, as these factors can also contribute to shifting issues and vibrations.
Possible Causes
Most common causes (ordered by frequency):
- Engine Mount Failure: The primary engine mount is confirmed broken, leading to excessive engine movement during gear engagement. A broken mount can result in harsh vibrations felt throughout the vehicle, particularly at idle when the engine's natural balance is disrupted. The lower torque mount is also prone to wear and should be inspected for any signs of damage or deterioration. Typical failure symptoms include increased vibrations and noise during acceleration or deceleration, especially noticeable when the vehicle is stationary. - Visible damage to the engine mount, increased vibrations at idle, harsh engagement into gear.
- Transmission Mount Issues: The transmission mount may also be contributing to the vibrations and jerking felt when the vehicle is in gear. Similar to engine mounts, worn or damaged transmission mounts can allow excessive movement of the transmission, leading to harsh engagement and vibrations. Inspection of the transmission mount is essential, as it plays a critical role in stabilizing the transmission during operation. - Harsh engagement into gear, vibrations felt throughout the vehicle, potential signs of wear on the mount.
- Transmission Fluid Condition: If the transmission fluid is low or contaminated, it can cause slipping or harsh shifting, contributing to the overall vibration issue. Inspecting the fluid condition and level is crucial, as degraded fluid can also lead to operational inefficiencies and exacerbate existing vibration problems. - Slipping during acceleration, fluid appears dark or has a burnt smell, abnormal shifting patterns.
- Exhaust System Issues: The excessive vibrations observed from the exhaust system may indicate failing exhaust hangers or supports, which can lead to additional noise and vibration. Inspecting the exhaust system for any loose components or damage is necessary as it can amplify the vibrations felt throughout the vehicle. - Visible exhaust hangers in poor condition, vibrations felt more prominently at idle.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Initial Inspection: Begin with a visual inspection of the engine and transmission mounts to identify any obvious damage or wear. Check the condition of the engine mount that is being replaced and inspect all other mounts for signs of deterioration or failure. Pay particular attention to the rubber bushings for cracks or separation.
- STEP 2 - Fluid Inspection: Check the transmission fluid level and condition. The fluid should be bright red and free of debris or burnt smell. If the fluid appears dark or has a burnt odor, it may indicate contamination or overheating, requiring a fluid change.
- STEP 3 - Test Drive: Conduct a test drive to observe the behavior of the vehicle under various conditions. Pay attention to vibrations when the vehicle is in gear and at idle. Note any shifting irregularities and how the vehicle responds to acceleration and deceleration.
- STEP 4 - Exhaust System Check: Inspect the exhaust system for loose hangers or supports. Any excessive movement or damage to the exhaust components can amplify vibrations. Ensure all exhaust connections are tight and in good condition.
